The present invention relates to a method and apparatus for regulating the permeability of wrapping material for rod-shaped articles which constitute or form part of smokers' products. More particularly, the invention relates to a method and apparatus for regulating and maintaining at a desired level the rate of admission of cool atmospheric air into the column of tobacco smoke in a region which is preferably close to one end of a rod-shaped smokers' product, such as a plain or filter-tipped cigarette, cigar or cigarillo. Still more particularly, the invention relates to a method and apparatus for regulating the permeability of wrapping material for rod-shaped smOkers' products in a manner such as to insure that the permeability of the wrapper of each and every product which leaves the maker (or at least the great majority of the products) will exhibit an optimum permeability.
Rod-shaped smokers' products having wrappers with so-called climatic zones (i.e., with zones which are perforated in order to permit entry of cool atmospheric air into the column of tobacco smoke) are becoming increasingly popular. In fact, many manufacturers of cigarettes or the like demand that each machine for the making of plain or filter tipped cigarettes or analogous smokers' products be equipped with apparatus which serve to perforate selected portions of the wrappers, preferably in a region close to one or both ends of a plain cigarette or in a region close to (and including) the mouthpiece of a filter-tipped rod-shaped smokers' product. The admission of cool atmospheric air into the column of tobacco smoke influences the percentage of nicotine and condensates. In addition, the admitted atmospheric air reduces the temperature of the smoke column.
The aforementioned commonly owned U.S. Patent of Wahle et al. discloses a method and apparatus for automatically regulating the permeability of wrapping material for rod-shaped smokers' products by testing the finished or partly finished rod-shaped articles for permeability of their tubular wrappers and by regulating the operation of perforating means in dependency on the results of testing. The perforating means may include needles, punching tools, one or more spark generators, one or more lasers or a combination of these. The perforating means can be placed adjacent the path of a continuous rod which is to be subdivided into discrete rod-shaped articles, adjacent the path of discrete rod-shaped articles, or adjacent the path of the web which travels toward the wrapping station. The regulating step includes comparing signals which are furnished by the testing unit with a reference signal and adjusting the perforating means when the intensity or another characteristic of test signals deviates from the same characteristic of the reference signal.
The testing unit is located downstream of the wrapping station or stations, i.e., at a location which is remote from the perforating means, especially if the perforating means is adjacent the path of the web which is about to be draped around one or more rod-like fillers. Consequently, if the permeability of the wrappers forming part of articles which arrive at the testing station is unsatisfactory, a substantial number of articles will have to be discarded in order to prevent their entry into storage or into a packing machine. For example, if the perforating means is adjacent the path along which the web of cigarette paper moves from a source to the wrapping station of a cigarette maker, and if cigarettes which are produced by the maker are thereupon admitted into a filter cigarette making machine which assembles plain cigarettes with filter plugs to form filter cigarettes, the testing unit is normally adjacent the path of filter cigarettes. Therefore, when the testing unit detects the presence of filter cigarettes whose wrappers are defective because the permeability of their material is excessive or insufficient, the entire series of plain cigarettes and filter cigarettes between the loci of the perforating means and testing unit is defective. Furthermore, certain makers of rod-shaped articles which form part of smokers' products are not invariably equipped with testing units. Typical examples of such makers are machines for the production of filter rods; the rods are severed to yield filter rod sections of desired length and the sections are introduced into a machine for the production of filter cigarettes, cigars or cigarillos. Thus, a very long series of filter rod sections can comprise wrappers whose porosity is unsatisfactory, and the defects will be detected only subsequent to admission into the next machine, e.g., into a filter cigarette maker. This can result in the production of extremely large numbers of defective smokers' products, especially in modern high-speed production lines which are designed to turn out up to and in excess of 70 smokers' products per second.